1. Field of the Invention
The present invention relates to a heat treating method. In particular, the present invention relates to a heat treating method for a golf club head.
2. Description of Related Art
Heat treating methods for a golf club head generally comprise vacuum heat treatments and high-frequency heat treatments. In a vacuum heat treatment, the whole golf club head is placed in a vacuum heat treatment furnace. Heat treatment on a particular portion of the golf club head is impossible. Further, in a case that the golf club head consists of at least two materials, the vacuum heat treatment furnace can proceed with heat treatment of only one of the materials. The properties of the other materials cannot be fully utilized. In a high-frequency heat treatment, high-frequency waves are used to proceed with local heat treatment on a particular portion of the golf club head. However, it is difficult to precisely control the temperature, the treating path, and the position of heat treatment, failing to provide uniform high-frequency heat treatments.
U.S. Pat. No. 6,776,726 discloses a golf club head comprising a ball striking face provided with a central region and a peripheral region surrounding the central region. A solution heat treatment and an aging treatment are made for the entirety of the golf club head basal body. Then, a peripheral heating treatment is made on the peripheral region by irradiating a high-energy laser beam until the surface hardness of the peripheral region is in a range of from 0.45 to 0.9 times the surface hardness of the central region. However, a portion of the surface in the heat treating zone of the peripheral region may melt and thus collapse, generating cavities, depressions, dimples, or the like during the laser treatment and adversely affecting the qualified product ratio. The irradiating time and the irradiating intensity of the high-energy beam have to be reduced to eliminate or mitigate the above problem, leading to limitation of the irradiating time, the irradiating intensity, and the depth of the heat treatment.